SU941898A1 - Beta-alanin quantitative determination method - Google Patents

Description

(5) METHOD FOR QUANTITATIVE DETERMINATION OF fi -ALANINE

one

The invention relates to the quantitative determination of / -alanine used in the production of amino acids, in addition, p) -apanine is used in medicine, biology and biochemistry, and the accuracy of determination of / -alanine contributes to the purity of the final product.

Polygraphic and spectroscopic ({lautometry methods for determining P-alanine, o

However, these methods are not very selective and require sophisticated equipment.

A titrimetric method for determining p-alanine hydro-5 with sodium oxide 31 is also known.

The method is limited to the analysis of pure {L-alanine, however, in mixtures with ammonium salts, strong bases, and secondary and tertiary amino acids 20, determination is impossible, since the impurities mentioned distort the results of the analysis.

The closest technical

Essentially to the proposed method is the quantitative determination of p-alanine by potentiometric titration of the amino group in a mixture of acetonitrile and acetic acid in a volume ratio of 5: T perchloric acid solution in methyl ethyl ketone. The determination according to a known method is as follows: a portion of alanine 0.03-0.04 g is dissolved in acetic acid, acetonitrile is added to a volume ratio of 1: 5, a pair of electrodes is dipped (glass and calomel), potentiometrically titrated to 0, 1 and. solution of perchloric acid in methyl ethyl ketone until a clear potential jump appears on the titration curve. Relative error of determination (-alanine is, 1. A mixture of p-alanine with secondary and tertiary amino acids, ammonia, alkalis and acids cannot be determined. The disadvantages of this method are low selectivity due to the impossibility of using the method for determining -alanine in the presence of secondary and tertiary amino acids, ammonia, alkalis and strong acids, since these compounds react with the titrant or p-alanine. The purpose of the invention is to increase the selectivity of the determination. Thus, in the method of quantifying P-alanine, a portion of fi-alanine in water is treated with 0, M solution of benzaldehyde in dimethyl sulfoxide at pH 10.5-11, followed by titration of unreacted benzaldehyde with hydroxylamine hydrochloride solution in dimethyl sulfoxide in the medium containing dimethyl sulfoxide in the medium containing dimethyl sulfoxide in a medium containing dimethyl sulfoxide in a medium containing dimethyl sulfoxide and hydroxylamine hydrochloride in dimethyl sulfoxide in a medium containing dimethyl sulfoxide in a medium containing dimethyl sulfoxide and a hydroxylamine hydrochloride solution sodium hydroxide solution at their volume ratio of 1-1.5: 1, respectively. Increasing the selectivity of the determination by expanding the definition. V-alanine ° in various mixtures is achieved by Wie specific reaction of the amino group E-alanine with benzaldehyde and benzaldehyde selective reaction with the titrant residue. Benzaldehyde reacts with the amino group (-alanine, and with secondary and tertiary amino acids, ammonia, alkalis and acids do not affect. Using a solution of benzaldehyde in dimethyl sulfoxide and carrying out the reaction of benzaldehyde with p-alanine at pH 10, 0 ensures the quantitative passage of the reaction in 20-25 minutes Increasing the pH of the medium during the interaction of 1H-alanine with benzaldehyde leads to the polymerization of benzaldehyde and distorts the results, and lowering the pH slows down the reaction. preference for other aldehydes and provides a specific reaction with p-alanine. in reaction with aldehyde. Use as a titrant a solution of hydroxylamine hydrochloride in dimethyl sulfoxide and as a solvent for a mixture of 3 / aqueous solution Sodium hydroxide with dimethyl sulfoxide in a volume ratio of 1: 1-1.5 creates conditions for the selective and quantitative titration of benzaldehyde, accompanied by a pronounced jump in potential at the equivalence point. The presence of secondary and tertiary amino acids, ammonia, ammonium salts, acids and alkalis does not affect the definition of p) alanine. Thus, the proposed method is as follows: a portion of the sample to be analyzed, containing 0 ,, g of f-alanine, is dissolved in 5 ml of distilled water, 5 ml of a buffer solution with a pH of 10.5-11.0 is added; 10; 0 ml 0.15-0.2 M. a solution of benzaldehyde in dimethylsuperoxide and mix for at least 30 minutes. Then 20-30 ml of a mixture of water with dimethyl sulfoxide in the ratio 1: 1.5-2 by volume are added, then a ml of an aqueous solution of sodium hydroxide is added just before titration. A pair of electrodes (platinum and calomel) are immersed in the solution and potentiometrically titrated with a 0.1-0.15 M solution of hydroxylamine hydrochloride in dimethyl sulfoxide until a potential jump appears on the titration curve. Simultaneously, idle experience is performed, i.e. titrate 10.0 ml of a 0.150, 2 M solution of benzaldehyde in dimethylsulfoxy. According to the difference in the amount of titrant consumed for titration of the blank experiment and analysis, the amount of benzaldehyde consumed in the reaction with -alanine and, accordingly, the amount of rgalanine are found. Example i. Quantitative determination of alanine. A weighed portion of p-alanine 0, an OPC g weighed with an accuracy of ± 0.0002 g was placed in a titration flask with a 100 ml section in 5 ml of distilled water, and 5 ml of a buffer solution of pH 11.0 prepared from sodium tetraborate was added. and sodium hydroxide, and 10.0 ml of a 0.15 M solution of benzaldehyde in dimethyl sulfoxide. The flask is closed with a stopper and allowed to mix on a magnetic stirrer for 30 minutes. At the same time, a blank experiment is prepared: 5 ml of distilled water, 5 ml of buffer solution and 10.0 ml of 0.15 M benzaldehyde solution are placed in a titration flask and allowed to mix for 30 minutes. Then, 30 ml of a mixture of water with dimethyl sulfoxide in a volume ratio of 1: 2 is added to the solutions and immediately before titration, k ml of a 30% aqueous solution of sodium hydroxide is added. A pair of electrodes (platinum and calomel) are immersed in the solution and potentiometrically titrated with a 0.1038 M hydroxylamine hydrochloride solution in dimethyl sulfoxide until a potential jump appears on the titration curve. The titrant consumption for the titration of the blank was AND, 41 ml, and the titrant consumption and titration of the analysis was 10.50 ml. A-alanine content is calculated as U (.o80.08302 X - - - X 100 99.6% Standard deviation is ± О, 9 Alanine theoretically contains 5-50% p-alanine, 45-50% secondary and tertiary amino acids and 5 10% water. A portion of the condensate 0.1035 g is weighed, placed in a titration flask, dissolved in 5 ml of distilled water, 5 ml of a buffer solution with a pH of 10.7 prepared and

p) -alanine

p) - alanine + ammonia O, 6

p) - alanine + sodium hydroxide 0,

(L-alanine + sulfuric acid 0.05113

0, OPA - 0.9 0.0433 + 1.0

0.0409

1.0 1.0 0.0405 ammonia and ammonium chloride and 10.0 ml of 0.2 M benzaldehyde solution in dimethyl sulfoxide. The flask is closed with a stopper and allowed to mix on a magnetic stirrer for 30 minutes. Parallel to the idle experience. Then, 20 ml of a mixture of water with dimethyl sulfoxide in a ratio of 1: 1.5 by volume is added to the solution, and immediately before titration 4 ml of 3% aqueous sodium hydroxide solution is added. A pair of electrodes are immersed in the solution and titrated potentiometrically with a 0.1476 M solution of hydroxylamine hydrochloride in dimethyl sulfoxide. The consumption of titrant for the blank titration is 13.55 ml, and during the titration of the analysis, respectively, 9.76 ml. A-alanine content calculated X - il3i5i: 3j6ioa4z6: 0 o8209. 0.1035 X 100 4B, 1. The deviation is equal to jt 1 0. The table shows the results of the determination | -alanine hydrolysates and a capacitor produced by p-alanine and some mixtures of i-alanine with acids and alkalis according to the proposed method. To establish a pH of 10.5-11.0, buffer solutions were tested: netrio tetraborate 5; - sodium hydroxide, ammonia - ammonium chloride and trimethylamine - trimethylamine hydrochloride. Titration is carried out potentiometrically using platinum (indicator) and saturated calomel electrodes with hydroxylamine hydrochloride in dimethyl sulfoxide.

Claims (1)

Claim A method for the quantitative determination of ^ -alanine by potentiometric 35 titration in a mixed solvent medium, characterized in that, in order to increase the selectivity of determination, a sample of β-alanine in _: water is treated with a 0.15Ό, 2 M solution of * 0 benzaldehyde in dimethyl sulfoxide at pH 10.511, 0 followed by titration of unreacted benzaldehyde with a solution of hydroxylamine hydrochloride in dimethyl sulfoxide in a medium of * 5 de solvent containing dimethyl sulfoxide and a 5 "7% aqueous solution of sodium hydroxide in a volume ratio of 1 -1.5: 1, respectively.